Syntheses of 2-Aroyl Benzofurans through Cascade Annulation on Arynes.

The highly efficient and expedient route for the syntheses of 2-aroyl benzofurans has been developed via the cascade [2+2] followed by a [4+1] annulation on arynes. The overall transformation proceeded through the formation of ortho-quinone methide by the insertion of transient aryne into N, N-dimethylformamide and subsequent trapping with sulfur ylide. Moreover, this transformation has a broad range of substrate scope with a high functional-group tolerance. This new reaction was successfully utilized in the synthesis of the potent CYP19 aromatase inhibitor and late-stage functionalization on the bioactive complex estrone.